An electrophotographic image forming apparatus forms an electrostatic latent image in such a manner that, after a rotating photoconductor is uniformly charged by using a charger, the surface of the photoconductor is exposed to light in accordance with image data. The image forming apparatus develops the electrostatic latent image by using toner, and transfers, onto a sheet, the toner image obtained through development, and fixes the toner image. The image forming apparatus employs a configuration in which such an image formation process is used to print a desired image.
In an electrophotographic system, non-uniformity in density of a toner image formed on a sheet may occur in the rotation axis direction of a photoconductor. This non-uniformity occurs due to variations in the light amount with which an electrostatic latent image is formed on the photoconductor or variations in light sensitivity of the photoconductor surface.
To suppress such density non-uniformity in the rotation axis direction of a photoconductor, the following configuration has been proposed in the patent literature. Multiple test patterns are printed in the rotation axis direction of a photoconductor on a sheet. The sheet on which the test patterns are printed is fed again, and the test patterns are read by using a density sensor disposed on a paper conveying path. The laser beam amount is adjusted at each of the positions in the main scanning direction on the basis of the read density.
Japanese Patent Laid-Open No. 2011-133771 describes such a process.
When a test image is formed on a sheet with a size smaller than that of a photoconductor in the rotation axis direction of the photoconductor, density is not corrected in areas outside the range in which the test image is formed.
Therefore, there is a need for an image forming apparatus which corrects density in areas outside the range in which a test image is formed.